Electric percussive tool



April 8, 1930. c. s. WEYANDT' vELEGTRIC PERCUSSIVE TOOL Filed March so, 1925 '3 sheets-shat 1 ATTORNEY c. s. WEYANDT 1,753,454

ELECTRIC PERCUSSIVE TOOL 7 Filed Mafch so 1925 :5 Sheets-Sheet 2 April 8,1930.

m ENTOR @r/ 74nd? ATTORNEYY April 8, 1930.

c, s. WEYANDT ELECTRIC PERCUSSIVE TOOL Filed March so. 1925- s Sheets-Sheet s mm a HH v 8m 0% mm mm Q Q i \S 2 E w mu mu b Mm Q 2w 3 m2 nlllll .3 v mm mm INVENTOR Caf/ M dfl TTORNEY Patented Apr. 8, 1930 UNITED STATES PATENT OFFICE CARL S. WEYANDT, OF PITTSBURGH, IPENNSYLVANIA, ASSIGNOR '10 CENTRAL ELEC- TRIO TOOL COMPANY, A. CORPORATION OF PENNSYLVANIA ELECTRIC rnncussrvn 'roor.

Application filed March 30, 1925., Serial No. 19,311.

My invention .relates to reciprocating motors and particularly to electrical motors of the reciprocating type. a

One object of my invention is the provision of a member within which the movable element of a motor reciprocates, said member supporting at its opposite ends clamping plates for positioning stationary elements of said motor. I

Another object of my invention is to provide a core of novel construction to reduce the electrical losses occurring within the motor.

M invention further resides in apparatus of. t e character hereinafterdescribed and claimed.

A still further object of my invention is to provide a reciprocating electric motor embodying the foregoing features which shall be simple in construction and cheaper to manufacture than the present types.

In electric hammers of the reciprocating motor type, it has been customary to rovide a resilient backstop for the reciprocating element, to be engaged thereby at or about the end of the path of travel of the element, to absorb its kinetic energy and to preclude the impression of large impact stresses upon the hammer structure. Such backstops were provided with helically-wound heat-treated springs which were properly supported and disposed in the path of the impact element. There -were several disadvantages in that structure. It seems that the duration of the impact forces impressed upon the spring was so short that the stresses set up were not distributed throughout the entire spring but instead were concentrated upon the first, or the first and second convolutions. Relatively large springs were consequently required which correspondingly increased the sizeand weight of the cooperating elements constituting the backstop. This alone, however, was not the only disadvantage.

Due to the concentration of the impact forces at the impact receiving end of the spring, considerable breakage occurred in springs that were not properly heat treated or that had inherent mperfections. Inasmuch as the remainder of the spring still presented a resilient buffer to the reciprocat ing element, it was diflicult for the operator to determine whether or not this trouble was in the spring or elsewhere in the hammer equipment. This necessitated dis-assembling the hammer to remove the backstop. While this was not a difficult operation, it required considerable time.

The helical spring and the component parts that constitute the backstop were made of steel and were heat treated. Since they were disposed at the end of the path of travel of the reciprocating core, adjacent the solenoid,

:they presented a path of diminished reluctance for considerable leakage flux. There was consequently a constant magnetic loss in the hammer which did not contribute to the; power or efiiciency of the hammer. In the prior hammers of the reciprocating motor type, the impact element constituted the core of two solenoids and was reciprocated thereby within a tube of non-magnetic material upon which ,the solenoids were supported. The core commonly employed was a solid cylinder of magnetic material. I have found that there was considerable loss of energy in the core due to eddy currents in the middle or along the axis of the core.

In the present structure, I provide a reciprocating element consisting of a cylindrical shell of magnetizable material mounted upon ,and secured to a rod or shaft of non-magnetizable material such as resistal. A hearing is disposed at each end of the tubular frame, and they support and guide the shaft of the reciprocating element to preclude friction between the core and the tubular frame. The area of the engaging surface is considerably less than in the types in which the core engages the tubular frame, and the friction is consequently diminished.

By means of the present construction, all ofthe foregoing disadvantages are obviated. Instead of a helical spring within the casing, I provide a plurality of leaf springs stacked in face to face relation and properly supported transversely across the axis in such position as to be engaged by the reciprocating element. The springs aresupported .on a saddle outside of the motor casing and extend through the opening of the handle. They are thus visible to the operator who can see immediately whether any of the springs are broken. It is also very easy to replace one of the leaf springsif it should be broken.

By removing the springs which are normally of heat treated steel and consequently of high magnetic retentivity, from the magnetic flux fields of the solenoid the magnetic losses are reduced. The mechanical losses are also diminished by reason of the decreased frictional surfaces of cngagen'ient between the core and the guides.

Since all the wear is limited to the core guides, they may be easily replaced by new guides when they become worn and the life of the motor is correspondingly increased.

In the accompanying drawings, Fig. 1 is a longitudinal view, partially in section, and partially in elevation taken along line 11 of'Fig. 3, of an electric motor embodying the features of my invention.

Fig. 2 is an end view in elevation of the handle end illustrating the disposition of the leaf springs that constitute the backstop.

Fig. 3 is a sectional view of the device illustrated in Fig. 1, showing the radial disposition of the magnetic field members.

Fig. 4 is a longitudinal view partially in section and partially in elevation of an electric motor of a different design embodying features of my invention.

Fig. 5 is a diagrammatic view of an elec-- trical circuit whereby the motor is energized during operation.

Fig. 6 is a longitudinal View partially in section and partially in elevation of an electric motor of modified design embodying features of my invention.

Fig. 7 is a side view partially in elevation and partially in section of the handle end of the structure of Fig. 6. I

As illustrated in Fig. 1, an electric motor 10 of the reciprocating motor type comprises two solenoids 11 and 12, that are supported upon a tubular frame 13 of non-magnetic material such as bronze. A movable impact member 14 is disposed within the tubular frame 13 and is actuated in response to the alternate energization of the solenoids 11 and 12. On its forward movement the impact element 14 strikes at tool 15 which is suitably disposed in the path of travel of the impact member 14. On its backward stroke, the impact member strikes a resilientbackstop consisting of a plurality of leaf springs 16. A casing 17 surrounds the solenoids and a front end plate 18 cooperates with the front end of the casing 17 to close the structure, and a handle unit 19 cooperates with the back end of the casing to cover the back end of the structure.

Magnetic circuit members 21, 22 and 23 a re radially disposed around the barrel to surround the solenoids 11 and 12, to conduct the flux of the respective solenoids and to concentrate such fluxes in a small region intermediate the ends of the respective solenoids.

.tance between the air gaps whereby there may be utilized a relatively shorter and lighter magnetizable core, making possible long and powerful strokes which are particularly advantageous in some fields of use. T lie-casing 17 is made of highly magnetic silicon steel and constitutes part of the magnetic circuit, being closely fitted over the ends of the laminations. hen the solenoids 11 and 12 are properly energized in alternation, the respective air gaps are traversed by highly concentrated magnetic fluxes which alternately operate upon the core to effect its reciprocation. Anchor plates 25 are secured to the barrel by bolts 26 and assist in holding the laminations in position. The anchor plates and the bolts 26 are of non magnetic material such as brass.

The impact element 14 comprises a cylindrical shaft 27 of non-magnetic material, such as resistal, and a cylindrical shell 28 of highlv' magnetic material such as silicon steel. The shell 28 is secured to the shaft 27 by suitable means such as rivet pins 29. The shaft 27 is supported and guided by two flanged bushing bearings 31 and 32 which are disposed at the respective ends of the barrel 13. The front bushing 32 is held in position by a tool holder 33 which is secured to the barrel 13 by athreaded nut 34 and a threaded lock washer-35. The nut 34 also serves to hold thefront end plate 18 in proper position against the tapered edge 36 of the casing 17.

Within the end plate 18 a threaded lockwasher 37 is disposed and held in position by a small screw 38, to back-up and support the laminations 23 and thrust them toward an anchor plate 25. At the rear end of the casing 17 there is a fibre washer 40 which engages the beveled edge of the casing and serves to impede transfer of heat from the electro-magnetic mechanism in casing 17 to the handle structure 19. Furthermore, washer 40 is somewhat deformable and hence acts to allow for unevenness of the parts that are clamped together. The washer 40 is held in position by a rear end cap 4]. which is threaded onto the barrel '13. The end cap 41 is provided with a flange 42 which engages a transverse base 43 that is integral with the handle 19, and serves thereby to lock the handle in fixed position with respect to the barrel. A spacing Washer 44 is disposed between the washer and the transverse base 43. A small screw in the flange 42 hind the springs toprotect the hand of the operator in case one of the springs should be broken. I

Within the end of the cap 41 is disposed a" threaded seating element 54 which accommodates an impact block 55, The seating element 54 is provided with a flange like por- 1 tion which serves as a seat for the impact block 55 which is disposed in the path of movement of the reciprocating impact member 14. In order to hold the bushing guide 31 in position, a'collar 56 is disposed between the flange of the guide 31 and the seating member 54 for the impact block. A look ring 57 is provided to prevent the seating member.

54 from moving out of its position in response to the repeated-blows of the moving impact member against the impact block 55.

When the reci rocating motor described above is assemble the spring 16 is put under an initial stress which serves to hold the elements of the spring tightly against the impact block 55 and also to reduce the extent of movement of the springs under the force of the impact blows of the reciprocating element.

When the solenoids are properly energized in alternation, the impact member 14 is reciprocated between the tool 15 and the impact block 55. When the tool is struck, it is caused to do useful work. When the impact block is struck, energy is stored in the springs and is returned to the movable member when it is re-actuated in a forward direction. The construction of the motor is such that it may be easily and readily assembled and taken apart.

In Fig. 2 is illustrated the disposition of the springs against the cross bar seating elements of the stirrups.

In Fig. 3 is illustrated the radial disposition of groups of the laminated field members of the solenoids.

In Fig. 4 is illustrated another modification of an electric motor in which the several parts are bolted together instead of being threaded together. I have found this particular construction advisable in larger and more powerful motors. As illustrated in Fig. 4, the tool holder 33 is disposed against the front guide bearing 32 to hold it in position and is so held against the guide bearing by means of a cross plate 60 and a collar 61. In this structure, the barrel 13 is not provided with the extra threaded portion and the threaded cap and lock washer are also obviated.

The rear guide bearing 31 is held in position by a washer 62 and a collar 63 which is held in position against movement by a unitary guide and clamping element 64. The element 64 is provided with a portion 65, which serves as a guide bearing, and a flange portion 66 which serves to hold the collar 63 in position, and also to lock the base 67 of the handle against movement. A cross plate 70 encircles the flange 66 and together with the cross plate 60 holds allof the motor elements in a compact unit by means of four bolts 71. Each pair of bolts supports the stirrup seating element 50 which is held in position by the lock nuts 72. s The springs disposed between the two stirrups are perforated at'the center to accommodate a positioning portion 73 of an impact element 74 which normally rests against the Washer 62. When struck by the core 14 the impact ele-' ment 74 moves within the bearing guide 65 against the springs 16. Impact element 74 has an oil chamber 7 4 at its core which .com-

municates through passages 74 and 7 4 with both the bearings for the core and stop members. A Washer of absorbent material 7 4, such as felt or the like, is resiliently positioned by spring 74 at the opening of said passages, thereby preventing too rapid supply of lubricant to. the bearings. Lubricant is supplied to chamber 74 through a spring oil nipple 73. The guard 53 prevents injuryto the operators hand in case one or more of the springs should break.

In Fig. 5 is illustrated a diagrammatic circuit which I prefer to use for the energization of the motor. Engergy is derived from an alternating current circuit and is supplied to the respective solenoids 11 and '12 through two electric valves 81 and 82 of the thermionic type, embodying an electron emitting filament as the cathode, and a plate as the anode. The filaments are energized from the secondary windings of a transformer 83, the primary winding of which is energized from the circuit 80. The filament of the valve 81 and the plate of the valve 82 are connected to one conductor 85 of the circuit through a trigger switch 84 which is disposed in the handle 19 and is subject to the control'of the operator. One terminal of the solenoid 11 is connectedto the filament of valve 82, and one terminal of the solenoid 12 is connected to the plate of valve 81. The other terminals of the .two

solenoids are joined and connected to the condu ctor 86 of the circuit.

Since the valves will conduct current only when the filament is negative With respect'to the plate, the valves will be alternately conductive to transmit current to the associated solenoids. Thus, when the conductor 85 is negative with respect to the conductor 86, the valve 81 will be conductive and will transmit current to the solenoid 12. At that time the valve 82 will be non-conductive since its plate is negative with respect to the filament. The solenoid 11 will therefore not be'energ'ized at that time. .lVhen the polarity of the circuit changes, however, and the conductor 85 becomes positive with respect to the conductor 86, the valve 81 will become non-conductive since its fiilamentis now positive with respect to the plate and no current will be transmitted to the solenoid 12. The valve 82 will now be conductive, however, since its plate is positive with respect to the filament, and the solenoid 11 will now be energized.

As the polarity of the circuit reverses, the valves become alternately conductive to transmit current alternately to the respective solenoids. These being alternately energized effect reciprocating motion of the impact member or core 14 to cause it to strike the tool by which useful work is to be done.

In the modification that is. illustrated in Fig. 6, the several parts of the motor are bolted together andthe'stresses upon the barrel are reduced to a minimum. As in the other modifications, the two solenoids are supported upon the barrel and laminated field members are employed to concentrate the magneticfiux within small annular regions intermediate the ends of the respective solenoids.

. The flanges of guide bearings 31 and 32 which are usually of suitable non-magnetic material such'as bronze, rest against the shoulders of each end of the barrel and are respectively provided with a concentricpocket which supports 21. treated wood bushing '90. The two shafts of the core ride in the wood bushings 90 and due to the character of these bushings no lubrication is required. In the other modications the bearing bushings are also of the self-lubricating type, containing graphite compositions. The non-magnetic guide bushing 31 is held in position against the barrel by a guide collar 91 which is restrained against movement by a resilient anchor plate 92 that is secured to the rear end plate 93 by two bolts 94. An impact element 95 extends into the collar or bushing 91 in the path of movement of the shaft of the core to be struck thereby. The back end of the impact portion 95 is provided with a flared shoulder which limi s its movement into the collar 91. The impact element 95 is normally held between the collar 91 and the springs 16. Core stop 95 furthermore provides means for lubricating a bearing of supporting shaft 106 by passage 95, which extends longitudinally and transversely of said core stop.

At the front end of the device the guide bushing 32 is held into position by the tool bushing 96 which is secured against movement by a resilient cross plate 97 secured to the front end plate 98 by two bolts 99. The

front and the rear end plates 98 and 93 are tightly secured by two rods '100 and 101 and serve to hold the casing in proper position. The supports for the spring 16 and the guard 53 are also disposed on the tie rods 100 and 101 and are properly secured thereto by suitable means such as the lock nuts 103.

By means ofthe structure that is illustrated in Fig. 6, considerable machine-work such as screw threading of the various parts, 1s eliminated and the motor is assembled and secured I The inner ends of the two shafts are reduced in cross section to provide shoulders 109. which may fit against the ends of the magnetic shell to limit the extent of their movement into the shell. The inner .ends of the shafts 106 and 107 are drilled out or hollowed outin any suitable manner to provide an end ring portion of diminished surface and strength. The inner portion of the shaft should be of sufiicient length to extend slightly into the channel region. A steel ball 110 is disposed between the twoshafts 106 and 107 when they are inserted into the shell 105 and when the two shafts are tightly pressed into the shell, the ends of the two shafts are distorted or spread by the steel ball 110 and caused to expand into the channel recess in the shell.

By means of this structure, the shell is tightly secured to the shafts and any relative movement bet-ween the shell and the shafts is prevented. As the shell is reciprocated in response to the alternate magnetic flux fields, the two shafts are caused to strike a suitable tool and the impact element in alternation.

Fig. is a side View partially in elevation and partially in section of the handle end of the motor illustrating the disposition and appearance of the external backstop. The ar- .case of breakage. Furthermore, the spring is removed from proximity to the magnetic fields of the solenoid and tendency to promote magnetic leakage is obviated. In addi- -tion, by means of the core structure and its operation, the mechanical friction losses of the motor are reduced to a minimum. Consequently, a greater efliciency is obtainable;

My invention is not limited specifically to the detailed construction that is illustrated since it may be variously modified without departure from the spirit and scope of the invention as set forth in the appended claims.

Structure for efiecting shorter space between air gaps is not herein claimed but is claimed in my application Serial No. 85,245), filed February 1, 1926, in whichare broadly claimed also the exteriorly disposed resilient buffer structure and the lubricating core stop. I claign as my invention: 1. An'electric motor of thereciprocatmg type comprising two solenoids axially disposed upon a tubular frame, a bearing removably mountedon each end of the frame, and a core responsive to the two solenoids and comprising two parts, one being a magnetic element actuable-by the solenoid flux and the other being a non-magnetic support. therefor and serving as a shaft movable within and between the bearings. 2. The combination with a reciprocating motor havinga reciprocating core system and a housing there or, of front and rearf end plates at each end of said housing, tie

rods for holdin said end lates fixed with respect to said busing, a ushing movable in each of said end plates, elements in sai bushings actuated by said core, and a resilient element secured to each of said end plates for coacting with its corresponding combination with a reciprocating core system and a housing therefor, of a member within which the core .stem moves, an end plate carried b each en of said member and through whic said member extends, and means urgin said plates toward said housing for seeurmg said plates in fixed relation with respect thereto.

4. A reciprocating motor comprising the combination with a reciprocating core system, of a member within which the core system moves, said member havin enlarged end portions, an end plate detacha 1y carried by each end portion for facilitating removalof said core system, and tie rod structure for securing said plates in spaced relation.

5. A reciprocating motor comprising the combination with a reciprocating core system, of a member within which the core system moves, electro-magnetic means comprising magnetizable elements for reciprocating said core system, a late carried by one en of said member, a ushing carried by said plate, and a member intervening between said magnetizable elements and bushing.

6. A reciprocating motor comprising the combination with a reciprocating core system, of a member within which the core sys-- i tem moves, electro-magnetic means comprisd scribed ing magnetizable elements for reciprocatin sa1d core system, a plate carried by one on of said member, a magnetizable bushing carried by 'saidplate, and a member of nonmagnetic material intervening between said magnetizable elements and bushing and carried by said member.

7. A reciprocating motor comprising a barrel, a system reclprocatory therein com-- actuated thereby comprising a magnetizable shell, non-magnetic members disposed in opposite ends of said shell, and a member wit in said shell adapted to engage adjacent ends of said members and hold said members in fixed relation to said magnetizable shell.

9. In a reciprocating motor, a movablecore system, a member within which said system moves, a guide bushing for said core system mounted within said member, and a bearing bushing of the oilless type mounted within said bushing.

In testimony whereof, I have hereunto submy name this 27th day of March,

CARL S. WEYANDT. 

